Magneto



arch 23 1926.; I 7243? I F. W. ANDREW MAGINETO Filed Oct. 11 1923 2 Sheets-Sheet l March 23,1926. I 577,437 7 F. w. ANDREW MAGNETO Filed Oct. 11, 1925 2 sheets-Sheet 2 Vi il/ I i Patented lVlar. 23, 1926.

UNITED STATES PATENT OFFICE.

FREDERICK W. ANDREW, OF GLEN HEAD, NEW YORK, ASSIGNOR TO EISEMAN N MAG NETO CORPORATION, OF BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

MAGNETO.

- Application filed October 11, 1923. Serial No. 667,950-

To all whom it may concem:

Be it known, that I, Fannnmon W. AN- DREW, a citizen of the United States, and a resident of Glen Head, Long'Island, county of Nassau, and State of New York, have invented certain new and useful Improvements in Magnetos, of which the following is a pole shoes and field magnet pole pieces, whereby the magneto operates at very low speeds to produce the necessary voltage.

- This is particularly advantageous in ignition 'magnetos for starting the engine.

Other features of my invention relate to an improved armature structure, a circuit breaker, and a Short circuiting device, as will be explained later on.

-My invention finds special application in magnetos of the so-called flywheel type,

although it is obviously not limited thereto.

The objects and advantages of my invention will be understood from 'a-detailed description of the accompanying drawings,

which --show a practical embodiment as actually constructed and operated.- In these drawings- 'Fig.-1 is a face view of a flywheel magneto embodying the features of my invention, a portion of the field magnet casing in section, showing the same mounted on one end of a crank-shaft; Fi 3 is a transverse section, approximate y on line 3-3 of Fig. 1, on an enlarged scaleq v i Fig. 4 is a fragmentary diagrammatic viewshowing one of the armature pole. shoes spanning the air gap of the field magnet;

Fig. 5' is a View similar-to Fig. 4, showing 7 the approximate position of the field magnet relatively to the armature pole shoes at the moment of sparking; v

Fig. 6 is a cross-section on line 66 of Fig. 1, on an enlarged scale, showing the short-circuiting contact spring on the hana Fig. 7 is a fragmentary view showing the split hub" on the armature disk for clamping the same on a suitable support;

Fi 8 is an enlarged fragmentary view on line 8-8 of Fig. 1, showing the cam which operates the circuit breaker; and

Fig. 9 is a transverse cross-section on line 99 of Fig. 6, showing the recessed form of the handle on the armature ,disk.

The outer framework of the magneto shown in the drawings consists of .a stationary disk or plate A and a rotary cy1indrical casing B. Member A is the armature disk, and B constitutes the field frame. As

shown in Fig. 2, one side of easing B is closed by a wall 1,iwhile the other side is 2, so that the members -A and B provide a substantially closed outer casing. These parts are formed of a suitable non-magnetic material, such as aluminum, and are preferably cast each in one piece.

On the inside of casing Bis mounted a ring-shaped permanent magnet M, which preferably fits snugly against the peripheral wall of the casing. The magnet M term1- nates at the points 3 and 4. To the polar ends of the magnet are attached ole pieces 5 and 6, which are preferably 0 soft iron. These pole pieces may be held in contact with the body of the magnet by any suitable means. outside of casing-B through the magnet into the pole pieces. The pole pieces 5 and 6 extend toward each other beyond polar ends 3 and- 4 of the magnet M and are separated by an air gap a, which is considerably shorter than the distance between the polar ends 3 and 4.. In the'particular machine illustrated in the drawings, the air gap a is about one-half thedength of a pole 5or 6, but this proportion is not essential. On the plate or disk A is mounted an armature comprising a core 8, on which is mounted a coil 9, and a pair of pole shoes 10 and 11 projecting from the ends of the core. It will be understood that the parts In Fig.1, screws 7 pass from the open, as indicated at 2. When the parts are assembled, the disk A fits into the opening- 8,110 and 11 are of suitable magnetic material. By this I mean material such as iron, which is readily susceptible to magnetic influence. The coil 9 may consist of a pri-. mary and a secondary winding, or it may be a single winding. I prefer to make the core 8 of a bundle of wires, the ends of which fit snugly into openings 12 in the pole shoes 10 and 11, as illustrated in Fig 1. The coil is machine-wound and after it is slipped on the core, the pole shoes are attached. This provides a very simple and cheap construction of armature, easily made and assembled, and yet having high magnetic efliciency. The pole shoes 10 and 11 may be of solid iron or composed of laminae. The entire armature structure is rigidlymounted in proper position .on the disk A by screws or rivets 13, which pass through the pole shoes, or in any other practical way. I

Attention is called to the fact that the pole shoes 10 and 11 have substantially straight inner sides 14, which terminate in polartips 15. The core space between the sides 14 of the pole shoes is of ample length to receive a coil with a sufiicient number of turns toproduce the required voltage in the operation of the machine. In magnetos of this type there is no room for a coil of large diameter, so the required number of turnsv must be obtained by increasing the length of the coil. Hence, the advantage of the Zarmature construction above described. The position of the armature is such that the pole pieces 5 and 6 of the revolving magnet move in close proximity to the curved polar faces 16 of the pole shoes.

The relation and proportion of the cooperating parts on the field magnet and armature are such that the polar tips 15 are sub- .stantially spanned by either pole piece'5 or 6, and the air gap a between the pole pieces .is substantially spanned by either ole shoe 10 or 11. This is clearly indicate in Fig.

4. As a result of this novel construction and piece 5 comes opposite the pole shoe 10. At

the same time, the other pole piece 6 moves across the pole shoe 11, with the result that the 'flux is suddenly and completely shifted through the coil. Fig. 5 indicates approximately the relative position of the parts at the moment of maximum induction, at which point the circuit is interrupted by the circuit breaker. If the magneto is used forig- 3000 revolutions per minute.

mary and secondary winding, and the resultant current will be of high voltage. If

the magneto is used for lighting purposes, i

the generated current will have a low voltage. These operations are well understood by the skilled engineer.

A magneto constructed as above described, produces ignition within a wide range of speeds. In practice I demonstrated that such a magneto operates satisfactorily on an engine running as low as 50 and as high as The circuit breaker contacts should be opened at the moment when the volume and ra idity of change of the magnetic flux throug the coil are substantially at a maximum. This point of break changes for diiferent speeds. The position of the parts in Fig. 5 is, therefore,

to be considered merely illustrative. In the particular machine shown in the drawings, I found that the moment of approximately greatest magnetic efliciency occurred when the trailing pole piece-of the magnet overlappedthe polar face of the nearest pole shoe to the extent of about /;ths of an inch, as indicated at m in Fi 5. This point will naturally vary with variations in the relative proportionsand dimensions of the magnetic pole pieces and armature ole shoes, but it can be readily determined in any particular design of machine by proper tests and trials,

as any electrical engineer will understand.

On the armature disk A is mounted a small late 17, which carries a circuit breaker inicated as a whole by R. The plate 17 is supported on a pair of studs 18extending inwardly from the armature disk'A. In orderto provide rotary adjustment of plate 17 on disk A, the plate is formed with arcuate slots 19, through which pass screws 20 for ti htening the plate in adjusted position. The purpose of-th'us adjusting the plate 17 is to determine the moment at which the circuit breaker is operated to open. the circuit of the coil, so that this breakshall occur at the moment of maximum induction in the coil as previously explained.

The circuit breaker R comprises a fixed contact 21 and a movable contact 22 pivoted on a pin 23 extending from plate 17. The contact 21 is'mounted in a small block 24 of insulatin material. I prefer to make this block of akelite, canvas or other similar material, which is strong and at the same time moistureroof and oil-proof. This avoids the use 0 fine and fragile insulating parts on one side of the con'tact. The insulatingblock 24 is fixed on plate 17 by small screws 25, or otherwise. The pivoted contact 22 is grounded to the metal plate 17, and is nor-. mally held against contact 21 by a coil spring 26 mounted on a stud 27 of plate 17. The spring 26 is preferably a flat helical spring so arranged that the free end 26.

is provided with: a handle 32, which is se- 29 of the field magnet casing B. The hub 29 is formed with a flange 30 for receiving rivets 31, or other fastening devices, by

means of which the hub is secured to the casing. Whenever the cam 28 strikes the rear end 'of'pivoted. contact 22, the contacts are interrupted. As pointed out, this break should take place substantially at the moment' when the armature coil 9 is subjected to the greatest magnetic influence.

The stationary armature disk A is so mounted that it can be readily adjusted in order to advance or retard the time of firing of the engine. For this purpose the disk cured to the disk by rivets 33, or otherwise.

After the armature disk has been moved,

to the desired position, it is clamped tight against accidental movement. This may be accomplished in any practical way. In the drawingsI have shown the disk A formed with a splithub 34 adapted to fit over. a

' circuit breaker.

boss 35 on the crank case 36. Broadly speaking, the boss 35 may be regarded as a support on which the armature disk may be radially adjusted and held in fixed position. The split hub 34 is provided with a screw 37 by means of which the connection "between the armature disk .and supporting boss 35 may be loosened and tightened as desired.

In the preferred form of my invention,

the handle 32- also constitutes part of-a shortcircuiting device, by which mean a device for short-circuiting the-circuit breaker when it is desired to put the magneto out of com-' mission, as for s'topping the englne. The

handle 32 is preferably curved at the sides to provide a shallow recess at one face thereof, as indicated at-32' in Fig. 9. At the base of the handle are fixed two insulating blocks 38 and 39, which are held in/place by rivets 40, or other fastening means. Between the insulating pieces 38 and 39 is clamped one end of a spring 41, wh ch is preferably in the form of a. flat str1p of phosphor bronze, or other suitable material. The insulated spring 41 iselectrically connected by a conductor 42 (shown in part in Fig. 6) to the insulated contact 21 of the The free end43 of spring 41 is. preferably bent toward the handle as shown in Figs. 6 and 9', so that only a slight movement of the spring is necessary to brlng it into contact with the handle. Since the sprin 41 extends alongthe dished or recessed side of the handle and is practically flush with the sides thereof, the mere grasping of the handle by the fingers will not press the "spring into short-circuiting position; In

other words, the spring 41 is not in the way the same time, the'spring 41 is easily accessible to short-circuit the circuit. breaker by simply pressing lightly against the spring,- whereby the curved free end 43 is brought into contact with the metal handle 32.

In practice the magneto may be mounted in any suitable position relatively to the engine. In Fig. 2, I have shown the magneto supported on the crank case 36 in such position that the rotary field frame is mounted directly on the projecting end 44 of the crank shaft 45, which passes through the boss or bearing hub 35. The field frame B is locked onthe engine shaft in any convenient 'wa In Fig. 2 there is a nut 46 engaging t e screw-threaded portion 47 of the crank shaft and having a flange 48 arranged to overlie the outer wall of the casing.

Although I have herein shown and described an ignition magneto of a specific construction, I will have it understood that I have done so merely to explain a preferred embodiment of my invention and not by way of limitation or restr1ct1on.

j I 013.1111 as my invention:

1. In a magneto, a ring-shaped permanent magnet having its polar ends separated, areshaped pole pieces mounted in contact with the polar ends of said magnet, said pole pieces being arranged to extend toward each other beyond'the polar ends of saidmagnet, a magnetic core provided atits ends with a pair of magnetic pole shoes-having substantially straight inner sides and curved polar faces, the polar faces of said pole shoes and the pole pieces of said magnet being shaped and arranged to rotate in close proximity relatively to each other, the distance between the inner sides'of said pole shoesbeing substantially spanned by either pole piece of the magnet, the olar faces of said pole shoes having eac a length substantially equal to the air gap between said pole pieces, and a coil mounted on said core between the inner sides of said pole shoes.

. 2. In a magneto, a rotary support, a ringshaped permanent magnet carried by said support, arc-shaped pole pieces mounted in contact "with the polar ends of said magnet on the inner face thereof, said polepieces being arranged to extend toward each other beyond the polar ends of said magnet, a stationary support,a magnetic core on said stationary support, said core being provided at its ends. 'With a pair of magnetic poleshoes having substantially straight inner sides and curved polar faces, the pole pieces of said magnet being arranged to move in close proximity to the polar faces ofsaid pole shoes, the distance between the inner sides of said pole shoes being substantially spanned by either pole piece of the magnet,-

the polar faces of said pole shoes having-10 FREDERICK W. ANDREW. 

